
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

    // 这个类用于去封装博客表的基本操作
    public class BlogDao {
        // 1. 往博客表里, 插入一个博客.
        public void insert(Blog blog) {
            // JDBC 基本代码~~
            Connection connection = null;
            PreparedStatement statement = null;
            try {
                // 1) 和数据库建立连接.
                connection = DBUtil.getConnection();
                // 2) 构造 SQL 语句
                String sql = "insert into blog values(null, ?, ?, ?, now())";
                statement = connection.prepareStatement(sql);
                statement.setString(1, blog.getTitle());
                statement.setString(2, blog.getContent());
                statement.setInt(3, blog.getUserId());
                // 3) 执行 SQL
                statement.executeUpdate();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                // 4) 关闭连接, 释放资源
                DBUtil.close(connection, statement, null);
            }
        }

        // 2. 能够获取到博客表中的所有博客的信息 (用于在博客列表页, 此处每篇博客不一定会获取到完整的正文)
        public List<Blog> selectAll() {
            List<Blog> blogs = new ArrayList<>();
            Connection connection = null;
            PreparedStatement statement = null;
            ResultSet resultSet = null;
            try {
                connection = DBUtil.getConnection();
                String sql = "select * from blog order by postTime desc";
                statement = connection.prepareStatement(sql);
                resultSet = statement.executeQuery();
                while (resultSet.next()) {
                    Blog blog = new Blog();
                    blog.setBlogId(resultSet.getInt("blogId"));
                    blog.setTitle(resultSet.getString("title"));
                    // 这里需要针对内容进行截断(太长了, 就去掉后面)
                    String content = resultSet.getString("content");
                    // 这个 50 纯属是随便定义的
                    if (content.length() > 60) {
                        content = content.substring(0, 60) + "...";
                    }
                    blog.setContent(content);
                    blog.setUserId(resultSet.getShort("userId"));
                    blog.setPostTime(resultSet.getTimestamp("postTime"));
                    blogs.add(blog);
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                DBUtil.close(connection, statement, resultSet);
            }
            return blogs;
        }

        // 3. 能够根据博客 id 获取到指定的博客内容 (用于在博客详情页)
        public Blog selectOne(int blogId) {
            Connection connection = null;
            PreparedStatement statement = null;
            ResultSet resultSet = null;
            try {
                connection = DBUtil.getConnection();
                String sql = "select * from blog where blogId = ?";
                statement = connection.prepareStatement(sql);
                statement.setInt(1, blogId);
                resultSet = statement.executeQuery();
                // 此处我们是使用 主键 来作为查询条件的. 查询结果, 要么是 1 , 要么是 0.
                if (resultSet.next()) {
                    Blog blog = new Blog();
                    blog.setBlogId(resultSet.getInt("blogId"));
                    blog.setTitle(resultSet.getString("title"));
                    blog.setContent(resultSet.getString("content"));
                    blog.setUserId(resultSet.getShort("userId"));
                    blog.setPostTime(resultSet.getTimestamp("postTime"));
                    return blog;
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                DBUtil.close(connection, statement, resultSet);
            }
            return null;
        }

        // 4. 从博客表中, 根据博客 id 删除博客.
        public void delete(int blogId) {
            Connection connection = null;
            PreparedStatement statement = null;
            try {
                connection = DBUtil.getConnection();
                String sql = "delete from blog where blogId = ?";
                statement = connection.prepareStatement(sql);
                statement.setInt(1, blogId);
                statement.executeUpdate();
            } catch (SQLException e) {
               e.printStackTrace();
            } finally {
                DBUtil.close(connection, statement, null);
            }
        }


    }

